I like to check what signal I may get from the RTL-SDR dongle via gqrx or SDR#, but I did not found a tool to do that on RPi. Recently I come across the “Raspberry Pi Freq Show RTL-SDR scanner” project ( learn.adafruit.com/freq-show-ra … r/overview ), but at first it did not work as I do not have the PiTFT. So I had to tweak the code a little bit to run the FreqShow on RPi 2 via RDP. PM me if interested.
I had a spare Pi so went through the install and it all installed fine.
pi@raspberrypi ~ $ rtl_tcp -a 192.168.1.253 -p 1234
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000001
Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
[R82XX] PLL not locked!
Tuned to 100000000 Hz.
listening...
Use the device argument 'rtl_tcp=192.168.1.253:1234' in OsmoSDR (gr-osmosdr) sou rce
to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).
client accepted!
set direct sampling 0
Disabled direct sampling mode
set freq correction 0
On my tablet I installed SDR Touch and the driver from the Google Play store
SDR Touch has a menu option of selecting a Networked URL, it is called Open.
Just put in the IP address of the RPi and the port you selected above eg 192.168.1.253:1234
Some gotchas
I couldn’t get it to work with wireless on the RPi so had to connect via ethernet.
Direct connection of the dongle to the RPI didn’t work so I used a USB hub.
The antenna needs to be a good one for the frequency you want to listen to. I wanted to listen to my local control tower on 127.15MHz so I connected it to my 5 element FM yagi on the roof. It comes in loud and clear.
I had to fiddle with the Gain on SDR Touch. I have it set to Auto AGC.
Not all phones and tablets will work, so check the free version first before you purchase it.
I get some strange looking waterfalls so I just stop and start SDR Touch.
If you have a Windows machine then it works with SDR Sharp (SDR#) also. Lots of fiddling with sample rates, gain settings and squelch.
I can’t offer any sort of support for this as I only follow instructions without knowing what I’m doing
Just added a second dongle to one of my FllightAware RPis and used the following command
rtl_tcp -a 192.168.1.110 -p 1234 -d 1
All seems to be running at the moment. rtl_tcp adds about an extra 10% CPU.
Edit} Sorry forgot to say that you don’t need to do the install in my post above if you are already feeding FlightAware as rtl_tcp is already installed.
How does the RPi know which dongle is which? How are they addressed? I used the command rtl_tcp -a 192.168.1.110 -p 1234 -d 1 to use the second dongle I’d just attached. If I attach a third dongle do I just use -d 2?
Is there a way to start/stop rtl_tcp once I have the process automatically starting as part of the startup process?
[EDIT] For those of you who use SDRTouch, is there a way to store the url permanently behind the “Open” button? It goes back to a default setting each time I restart the app. I have paid my $10 for the full version.
Quite a while ago I tried running multiple rtl_tcp daemons at boot via individual init.d scripts, cant find the scripts right now but it was a bit to unstable on my old OPI system (pre Armbian) so I went back starting and stopping from a ssh terminal. It may well be a bit more stable on Raspberrian so your mileage may vary.
Up to you! I have done around 6 so far with no problems but my dongles are all the cheap $10 variaty so im never too worried and it’s worth it be able to simply distinguish between dongles on a remote server.
There are stories of the eeprom writes going bad over on https://www.reddit.com/r/RTLSDR/ but have never really looked into the circumstances.